This study directly responds to the NIMH Notice of Information on High-Priority Areas for Research on Women's Mental Health During Pregnancy and the Postpartum Period (NOT-MH-15-013). Perinatal mood and anxiety disorders (PMAD), which includes depression and/or anxiety in the year before or after delivery, are common complications of pregnancy, affecting up to one in five women, with costs over $15 billion per year in the US. PMAD can negatively affect mothers, babies, and families beyond the perinatal period, and have lasting clinical and economic effects. PMAD treatment can improve maternal and neonatal health outcomes, yet mental health (MH) services are rarely used. Over the past decade, federal health legislation, such as the Mental Health Parity and Addiction Equity Act of 2008 (MHPAEA), and subsequent federal legislation affecting MH benefits (henceforth, MH policy changes), provided one of the largest expansions of MH coverage in a generation, by increasing coverage and extending federal parity protections to more than 60 million Americans. The MH policy changes require that all commercial, employer-based health plans cover MH services, and prevent higher levels of cost-sharing for MH relative to medical/surgical care. To inform future policy and clinical interventions, it is imperative to understand the clinical and economic effects of unprecedented extensions of MH coverage during the perinatal period. This study will take advantage of the natural experiments of federal MH policy changes. We propose to study the impact of MH policy changes in a large and diverse national sample of women during the perinatal period enrolled in employer-based insurance using Optum? Clinformatics? Data Mart (Optum). In this proposed four-year study, we will use patient-level analyses of women with diagnosed PMAD to examine the association of mandated federal MH policy changes with: 1) changes in MH utilization and outcomes (psychiatric assessment, psychotherapy, psychotropic medication use, diagnosed self-harm, suicide attempts, and/or suicidal ideation) and overall utilization (outpatient visits, inpatient stays, emergency department visits, and readmissions) in the year before and year after delivery; 2) changes in delivery outcomes (severe maternal morbidity, preterm birth, and caesarean delivery rates); and 3) changes in MH expenditures and overall expenditures in the year before and year after delivery. For each aim, we will conduct subgroup analyses to examine the differential effects of MH policy changes on: 1) women in states with stronger vs. weaker pre-existing parity laws, 2) self-insured plans vs. fully insured plans, 3) income subgroups, and 4) race and ethnicity groups. Given the dearth of perinatal MH services research, and the high, inter-generational costs of ineffectively managed PMAD, this innovative, large scale investigation will provide necessary evidence for future policymaking and clinical intervention efforts that could influence pregnancy, delivery-related, and downstream clinical and economic outcomes for this vulnerable and high-cost population of women and their children.